ISSN:0920-5071    

DOI:10.1163/156939393X00589

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

We proposed a superresolved "Wave CT" which utilizes fundamental properties of the wave, i.e. diffraction, refraction, reflection, and attenuation. It solves the Helmholtz equation which has a complex wave number including both refractive index and attenuation coefficient, and reconstructs superresolved complex images of the objects. The fundamentals of the wave CT are the following two points: first, the wavelength of the wave used is much longer than the structure of the object to be imaged; second, the phase information of the wave traveled through the object contributes much more to the image reconstruction than the amplitude information. Just as the X-ray CT is the extremum of the short-wavelength imaging, which may be called "Particle CT," the wave CT is the extremum of the long-wavelength imaging. Therefore, we named it "Wave CT." The mathematical method of the wave CT cannot be independent of itself, and we proposed a combination of FEM and BEM. It is not a perturbation method unlike the so-called diffraction tomography. Therefore, the dynamic range of the reconstructed image is unlimited in principle, but it is limited in practice by numerical problems. This paper reports a development of the numerical calculation, i.e. very exact and wide dynamic range images are reconstructed, which is relatively insensitive to the noise component of the projections. As an example, human body tomography by the wave CT is considered with radio wave of about 100MHz.

ISSN:0920-5071    

DOI:10.1163/156939393X00598

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In this work the active tomographic imaging of biological bodies which exhibits a high dielectric contrast is studied. Two approaches based on the Born approximation are presented: a differential reconstruction method which allows to visualize dielectric alterations and a matched synthesis method intended to minimize the distortion suffered by the illuminating field within the body. The presented techniques have been investigated by numerical simulations and experimentally in a cylindrical tomographic microwave system recently developed, considering the possible applications like Hyperthermia treatment monitoring in cancer.

ISSN:0920-5071    

DOI:10.1163/156939393X00606

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Under the Born approximation, the effect of view angle variations on image reconstruction in vector diffraction tomography is investigated. This paper deals with internal image reconstructions of infinitely long lossless and lossy dielectric cylinders placed in free space. Emphasis is placed on showing how both the co-polarized and the cross-polarized diffracted terms vary with incidence angle in the image reconstruction because any oblique incidence on a curved surface always produces depolarization. The cross-polarized component was found to contain object information on edges, i.e., the boundary position of the cylinder. It is shown that polarization utilization will play an important role in precise image reconstruction in microwave diffraction tomography.

ISSN:0920-5071    

DOI:10.1163/156939393X00615

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

This paper describes the experimental results on the subsurface radars developed by authors. Several new techniques including noise and clutter rejection techniques are introduced in order to develop a subsurface radar which has high target resolution, extended range and clear image. Experimental results are presented to demonstrate improved capabilities.

ISSN:0920-5071    

DOI:10.1163/156939393X00624

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A modal method is used for the determination of the near field weighting functions related to the power transmitted from a rectangular waveguide aperture towards a lossy material and, by reciprocity, to the corresponding radiometric signals created by the thermal noise emission. This method is applied to homogeneous or multilayered material, such as in microwave radiometry applied to medicine for non invasive thermometry of the subcutaneous tissues. From the knowledge of the weighting functions, we propose a new definition for the volume of material coupled with the probe, as radiometric measurement terms. We present examples of such coupled volumes, as a function of frequency or size of the probe.

ISSN:0920-5071    

DOI:10.1163/156939393X00633

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A method of retrieving a temperature-depth profile in biological object from a set of multi-frequency microwave radiometric data has been developed. The method is a combination of model-fitting and Monte Carlo techniques and is capable of estimating a profile and its confidence interval as a function of the depth. We use 2σ -intervals as a measure of the precision of tissue temperature measurements. The method was tested and supported by an experiment in which temperature distributions in a muscle equivalent agar phantom were measured using a 5-band, 1-3.8 GHz radiometer with the brightness temperature resolution of 0.05-0.07 K. A typical result of the experiment showed that 2σ -intervals were 1 K or less for 0 < z < 3 cm, 1.4 K at z = 4 cm, and 3 K at z = 5 cm. A numerical simulation study was made using this technique to assess effects of the selection of measurement frequencies, number of frequency bands, brightness temperature resolution of radiometer and thickness of fat layer on the precision. Results indicated that 2σ -intervals of about 1.0 K or less over a 0-5 cm depth range could be achieved by a 6-band, 0.55-3.8 GHz radiometer with the brightness temperature resolution of 0.05 K.

ISSN:0920-5071    

DOI:10.1163/156939393X00642

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Due to the interest in the non-invasive measurement of subcutaneous temperature, a four-frequency microwave radiometer system has been tested on a two-dimensional thermal phantom consisting of a hotter tube embedded eccentrically in a colder circular container simulating a cylindrical body region with an inhomogeneous temperature distribution. It is shown that measured radiometric data agree with a theoretical model of the electromagnetic radiation from thermal structures. An equation for retrieving temperature distributions in homogeneous circular cylinders has been obtained by taking regularity properties of temperature functions into account. Results of temperature reconstructions from both measured and synthetic data are reported showing the capability of the method.

ISSN:0920-5071    

DOI:10.1163/156939393X00651

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939393X00660

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939393X00679

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor